7 Answers
7

The best rule of thumb for punctuating in and around parenthetical remarks is that the sentence should be valid if you remove the parentheses and everything inside them.

Here I have an example (with a parenthetical remark).

Here is the same example (with the same remark, even.)

Removing the entire parenthetical remark from the first sentence still leaves me with a valid structure, while removing it from the second leaves me lacking any terminal punctuation; thus the first is correct.

How about this one: I like bananas (but why?). Period looks kind of extraneous there...
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StasMSep 14 '11 at 20:13

3

What about when emphasis is needed on the parenthetical statement, but not the entire sentence? e.g. The cops caught a thief (the one who stole your wallet!). Wouldn't you say the exclamation point goes inside the parenthesis then?
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boboboboJul 16 '12 at 0:06

Place the period logically when parentheses are involved. In the first example, the period goes outside because the single sentence ends after the parentheses. In the second example, it goes inside because it belongs to the second sentence.

Well, I prefer using the British logic for placing periods even though I'm not only American, but I live in Texas. Since I don't want to portray myself as an ignorant person, I think a lot of textual decency. While I place my periods outside the quotation marks, I'm left feeling haunted by the idea that an American might think I'm the ignorant one since I'm putting periods after closing quotes when the text being quoted is part of the structure of the sentence itself, not a dialogue in a story nor a quotation of a complete sentence.

Note that I wrote these sentences as examples of the rules they describe (in the first, the clause is dependent; in the second, it's independent.) I hoped they might serve as a bit of a mnemonic.
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MT_HeadJul 7 '12 at 5:49

What about the ending punctuation for the sentence in your second example? According to "The Grammar Bible" by Michael Stumpf, p. 537: "The punctuation for parenthetical items remains within the parentheses. Punctuate the primary portion of the sentence as if the parenthetical portion were not there."
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JLGJul 7 '12 at 19:54

@JLG - Taken at face value, that can lead to double punctuation, which is generally considered undesirable (what if the parenthetical portion is a question?). If that's not a problem for you, go with Stumpf.
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MT_HeadJul 7 '12 at 20:21

Yes, it does lead to double punctuation...which is what you did with your sentence in your reply to me. So why would you object to a period at the end of the second example sentence?
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JLGJul 7 '12 at 20:38

1

@JLG - I did that on purpose, as a demonstration. I dislike it; perhaps you don't. The rule I put forward is the one I learned in school, and the one I follow myself (when, of course, I'm paying sufficient attention). I am aware that there are other rules in circulation, such as Stumpf's. I don't agree with them, but I don't think it's a terribly huge deal: meaning and clarity are generally not lost either way.
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MT_HeadJul 7 '12 at 21:22